Specifications:Material: plastic + carbon steel ball + fishing lineSize: 18 * 14 * 11CMStyle:simple modernDescription:Not only demonstrates a pendulum, but shows the laws of conservation of impulse and energy.Friction and damping effects have also been observed.If one of the balls is lifted and allowed to fall back at one end, then one will swing out the same distance at the other end.This causes the beginning of perpetual motion which dies down due to the resistance of the air and friction, an interesting process to watch.It can be an exquisite decoration for home and office，An ideal gift for relatives and friends。Package Includes:1 x Shot Put Cradle (other accessories demo in the picture is not included.)Notice:Please allow 1-3cm error due to manual measurement and make sure you do not mind before ordering.Please understand that colors may exist chromatic aberration as the different placement of pictures.